Change screen breakpoint to hide hamburger menu

[alexmarqs]

Hi @iamsahilvhora,

First of all, thanks for your cool landing page examples using tailwindCSS.

Regarding your fair-rate-mortgage template (https://tailwindcss-templates.netlify.com/fair-rate-mortgage/), I found that for screen widths between 640px (sm) and 768px (md) there are no nav items available in your navbar: the hamburger menu is being hidden for breakpoint 'sm', however your navigation items are only being displayed for breakpoint 'md'. I have created a small pull request to correct this behaviour. Please have a look at it :).

Thanks and Regards, Alex